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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 15 Aug 2019 07:54:56 +0100 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x7F6stfi50921518 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 15 Aug 2019 06:54:55 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 68AA9A4060; Thu, 15 Aug 2019 06:54:55 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 31DEEA4054; Thu, 15 Aug 2019 06:54:54 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.8.59]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Thu, 15 Aug 2019 06:54:54 +0000 (GMT) Date: Thu, 15 Aug 2019 09:54:52 +0300 From: Mike Rapoport To: "Alastair D'Silva" Subject: Re: [PATCH 4/6] powerpc: Chunk calls to flush_dcache_range in arch_*_memory References: <20190815041057.13627-1-alastair@au1.ibm.com> <20190815041057.13627-5-alastair@au1.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190815041057.13627-5-alastair@au1.ibm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19081506-0028-0000-0000-0000038FF606 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19081506-0029-0000-0000-000024520BD9 Message-Id: <20190815065452.GB19609@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-08-15_03:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908150071 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Greg Kroah-Hartman , alastair@d-silva.org, David Hildenbrand , linux-kernel@vger.kernel.org, Nicholas Piggin , Mike Rapoport , Qian Cai , Paul Mackerras , Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, Andrew Morton , Allison Randal Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Aug 15, 2019 at 02:10:49PM +1000, Alastair D'Silva wrote: > From: Alastair D'Silva > > When presented with large amounts of memory being hotplugged > (in my test case, ~890GB), the call to flush_dcache_range takes > a while (~50 seconds), triggering RCU stalls. > > This patch breaks up the call into 16GB chunks, calling > cond_resched() inbetween to allow the scheduler to run. > > Signed-off-by: Alastair D'Silva > --- > arch/powerpc/mm/mem.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c > index 5400da87a804..fb0d5e9aa11b 100644 > --- a/arch/powerpc/mm/mem.c > +++ b/arch/powerpc/mm/mem.c > @@ -104,11 +104,14 @@ int __weak remove_section_mapping(unsigned long start, unsigned long end) > return -ENODEV; > } > > +#define FLUSH_CHUNK_SIZE (16ull * 1024ull * 1024ull * 1024ull) IMHO this begs for adding SZ_16G to include/linux/sizes.h and using it here > + > int __ref arch_add_memory(int nid, u64 start, u64 size, > struct mhp_restrictions *restrictions) > { > unsigned long start_pfn = start >> PAGE_SHIFT; > unsigned long nr_pages = size >> PAGE_SHIFT; > + unsigned long i; > int rc; > > resize_hpt_for_hotplug(memblock_phys_mem_size()); > @@ -120,7 +123,11 @@ int __ref arch_add_memory(int nid, u64 start, u64 size, > start, start + size, rc); > return -EFAULT; > } > - flush_dcache_range(start, start + size); > + > + for (i = 0; i < size; i += FLUSH_CHUNK_SIZE) { > + flush_dcache_range(start + i, min(start + size, start + i + FLUSH_CHUNK_SIZE)); > + cond_resched(); > + } > > return __add_pages(nid, start_pfn, nr_pages, restrictions); > } > @@ -131,13 +138,18 @@ void __ref arch_remove_memory(int nid, u64 start, u64 size, > unsigned long start_pfn = start >> PAGE_SHIFT; > unsigned long nr_pages = size >> PAGE_SHIFT; > struct page *page = pfn_to_page(start_pfn) + vmem_altmap_offset(altmap); > + unsigned long i; > int ret; > > __remove_pages(page_zone(page), start_pfn, nr_pages, altmap); > > /* Remove htab bolted mappings for this section of memory */ > start = (unsigned long)__va(start); > - flush_dcache_range(start, start + size); > + for (i = 0; i < size; i += FLUSH_CHUNK_SIZE) { > + flush_dcache_range(start + i, min(start + size, start + i + FLUSH_CHUNK_SIZE)); > + cond_resched(); > + } > + > ret = remove_section_mapping(start, start + size); > WARN_ON_ONCE(ret); > > -- > 2.21.0 > -- Sincerely yours, Mike.